Although his fellow enthusiasts are half his size, Stephen Phelan finds his inner warrior at the Iga Ninja Festival.

TO ARRIVE in Iga Ueno on the first Sunday in April is to feel like a stranger in ninjatown. This small city in the mountains, about two hours by train from Osaka, is supposedly the ancestral home of those fearsome feudal super-sneaks and master killers, whose name and reputation have spread across the world through movies, comic books and video games.

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Here in Japan, ninjas are now something of a national myth, a slightly cartoonish composite of old folk tales and modern pop culture.

Canine dress-ups. Photo: Reuters

This morning in Iga Ueno, however, it would be discourteous to dispute their existence. It's the opening day of the annual ninja festival and travel on public transport is free to anyone in costume. Connecting to the local loop line, I step on to a train brightly painted with ninja murals (designed by the famous Japanese manga artist Leiji Matsumoto) and find my carriage filled with muffled, hooded figures, all armed with swords and throwing stars.

Admittedly, their weapons appear to be made of soft foam or folded paper, and their outfits come in a range of colours - not just classic ninja black but purple, red, canary yellow, baby blue and a distinctly unthreatening shade of pink.

Also, very few of these mysterious commuters stand much over 120 centimetres tall. Apparently, only children take this occasion seriously enough to dress for it. The centre of town is overrun with excitable little death merchants, mostly around the 16th-century castle, where the moat and stone walls provide an ideal backdrop for springing mock assassinations on their parents.

As it happens, this sunny weekend also marks the beginning of cherry blossom season and the castle grounds are shaded by sakura trees, with families picnicking under the petals. Some have brought their dogs and these, too, are kitted out with hoods and swords.

Other festival activities include combat demonstrations at the Iga-ryu Ninja Museum (iganinja.jp/en). And life-size ninja mannequins have been positioned around town, staring blankly from the rooftops, peeking from behind telephone poles and lying under benches, more like modern drunks than mediaeval spies.

I spent much of my own childhood dreaming of this and resenting my parents for their failure to train me from birth in the lethal arts of the shadow warrior.

They permitted me to rent such silly yet illicit videos as Pray for Death and Revenge of the Ninja but drew the line at buying me the wicked-looking tools of the trade. "A ninja wouldn't whine like that," my father told me, twisting the knife. "The ninja is always adaptable."

Eventually, I accepted I would never be much more physically adroit than Winnie the Pooh but

I have never forgotten my early masters and have travelled the length and breadth of Japan to honour them.

Near Nagano, in the wooded alpine village of Togakushi, there is the Shinobi Karakuri Fushigi Yashiki (tinyurl.com/6hzamcf), or "ninja gimmickry wonder house". A maze of false floors, secret chambers and hidden passageways, it seemed kitsch and juvenile to me until

I got frantically lost inside for more than two hours and had to be rescued by an elderly attendant.

To the north, in Kanazawa, there is the so-called Ninjadera, a house and shrine that once belonged to the powerful local Maeda clan, who were not actually ninjas at all but devised such crafty and deadly defences that their home was recently renamed. Just adding the word "ninja" has proved a sure-fire way to bring in the tourists.

The word is, I am told by scholars, relatively new, "a product of the modern age and the entertainment industry". A guide at the museum in Iga Ueno, Kanako Murata, says the original clandestine operatives went by many different names and performed any number of functions. "Their chief role was to gather information," Murata says.

"Never to assassinate. In movies they are always killing people and viewers have come to believe these violent images. Our mission here is to tell them the truth."

This is the busiest time of the year at the museum, with long lines of visitors filing past their displays of old scrolls and rusty artefacts. The bulk of this material dates from the "warring states" period between the 15th and 17th centuries, when the rough terrain around Iga was rife with bandits, dissidents, ascetic mystics and rogue samurai, who all made their own contributions to ninja legend.

The exhibits make the case that the real shadow warriors were highly trained intelligence agents in the employ of rival warlords, rather than kung fu wizards who could vanish into mirrors and run across moonbeams on their tippy-toes.

If anyone is disappointed to hear this, they are soon distracted by the hourly combat show, by a troupe called the Ashuka. I have already suffered a fit of the giggles from reading this group's promotional poster, which proclaims in unfortunate English that their ninja forebears developed these skills while "living hidden on the backside of history". The show itself is a combination of martial arts, acrobatics, special effects and slapstick, with audience members invited to try their hand with a shuriken, or throwing star.

My first attempt goes into the dust, my second into netting at the back of the stage. My third strikes the edge of the target - not a killing blow, perhaps, but nasty enough to delight my childhood self and satisfy my inner ninja.

The streets of Iga Ueno are literally paved with ninjas, recast as friendly faced mascots and imprinted on manhole covers, bridges, buses and even fire engines. And local businesses are fairly upfront about the true purpose of the festival, having capitalised on this event since it started in 1964.

The Aikan-Tei noodle restaurant offers "ninja" udon and soba, and a ninja costume rental service on the side. The Miyazaki pickle shop sells "ninja" preserves.

I have no great hopes for the authenticity of the Murai Banko-en ninja cafe but owner Motoharu Murai claims a bona fide bloodline.

His grandfather was a ninja, he says, serving me brown tea and black sesame ice-cream in his courtyard garden. Then he disappears into a back room and bursts back out wearing a wig and firing a cap gun.

My shriek of fright is certainly un-ninja-like, and Muraimoto-san smiles to show he has taught me a valuable lesson. Further surprises follow, as he emerges in different disguises with more antique weapons from his arsenal - a pistol, a pike and a heavy iron rifle with ornate carvings on the barrel.

At last, out comes his grandfather's old katana.

"Dangerous," he warns, letting me heft the sword and telling me it has killed three people. As with most ninja stories, this is probably not true. But the blade feels very real.

The Iga Ninja Festival runs for five weeks from the first weekend in April, with events centred on the Iga-ryu Ninja Museum in Ueno Park, iganinja.jp/en. Jetstar flies to Osaka from Sydney, jetstar.com. Trains to Iga Ueno leave from Osaka Kansai airport.